Evaluation expérimentale de l'hydratation et du pouvoir occlusif in vivo et in vitro d'excipients lipophiles et de leurs émulsions phase huile continue

Resume Une etude a ete realisee sur trois emulsions eau dans huile et leurs phases grasses respectives, vaseline, huile de paraffine et huile d'amande douce, en vue de comparer leurs proprietes occlusives et par voie de consequence leur influence sur l'hydratation cutanee. Une methode in vitro utilisant des cellules de type ‘Patel’a permis dans un premier temps de classer les differentes emulsions et leurs phases grasses-en fonction de leur permeabilitea la vapeur d'eau, ce qui conduit par ordre croissant de degre d'occlusion a: huile d'amande douce, huile de paraffine et vaseline. Pour les etudes in vivo chez l'homme, l'influence de l'application des memes substances sur la perte insensible d'eau (PIE) et l'hydratation cutanee a ete mesuree avec un evaporimetre et un corneometre. Les differentes phases grasses, utilisees pures, augmentent l'hydratation par effet occlusif, ce phenomene etant objective par les mesures de PIE. Par contre pour les emulsions correspondantes, il semblerait que l'augmentation de l'hydratation ne fasse pas intervenir de mecanisme occlusif. Synopsis A study was carried out on three water in oil emulsions and their respective oil-phases, petrolatum, liquid paraffin and sweet almond oil, in order to compare their occlusive properties and thus their influence on cutaneous hydration. An in vitro method using ‘Patel’cells in a water-saturated atmosphere at controlled temperature enabled, in the first instance, the various emulsions and their oil-phases to be classified according to their permeability to water vapour. The results are in order of increasing degree of occlusion: sweet almond oil, liquid paraffin and petrolatum. In in vivo studies on human volunteers, the influence of the application of the same substances on transepidermal water loss (TEWL) and cutaneous hydration was measured with an evaporimeter and a corneometer, in a temperature and humidity-controlled room. Measurements were performed on the flexor side of the forearm after sodium lauryl sulphate 5% insult on six subjects at times of 0, 30, 120 and 270 min. The different oils, used pure, increased the hydration by an occlusive effect, and this was described by measurements of TEWL. On the other hand, after using the emulsions, the increase in hydration noted does not appear to involve an occlusive mechanism.